LANSING — Good news for Michigan vineyards: The time grapes have to ripen has dramatically increased over the past few decades.

“It’s nearly grown an entire month in just four decades,” said Steven Schultze, an assistant professor of geography at the University of South Alabama who discovered the shift as a doctoral student at Michigan State University. “Since 1971, the growing season in Southwest Michigan has increased by 28.8 days.”

Michigan has been growing grapes for a long time, mostly for juice and jams. It was only in the late 1960s that most of the state’s vineyards tried growing wine grapes, Schultze said.

Michigan has 15,000 acres of grapes, a fifth of them wine grapes, said Paolo Sabbatini, an associate professor with the MSU Department of Horticulture. That puts Michigan at fifth in the U.S. for acreage. It’s also among the top 10 wine producers in the country.

The reason for this shift is the change in climate over the past few decades. The study by Schultze found that there’s been a warming trend in Michigan, with warmer springs and more frost-free days.

“There are a million bad things that will and have happened with climate change,” Schultze said. “The thing is, this is a good thing.”

That extra month means a lot. Since there are more days for the grapes to ripen, varieties that take longer to ripen are now viable for Michigan vineyards, including more varieties of grapes for red wines.

“Michigan is known for growing excellent white wines,” Sabbatini said. “Whites are varieties that do not require a very long season. The problem in Michigan was always that we had challenges in growing reds, and in the U.S. most of the market for wines are in the reds.”

One reason why Michigan is good for grapes is the stability of its weather, particularly near the Great Lakes, Schultze said. Lake Michigan in particular prevents the temperature from dropping low enough during the winter and climbing high enough in the summer to kill the vines. Warmer spring temperatures cause the grapes to come out of dormancy sooner, which puts them at risk of a late frost.

The Michigan wine industry has grown since the 1970s, according to Michigan State University.

Photo courtesy RaeAllen (flickr)

“The bad news is that the wine grapes, they don’t handle frost well,” Schultze said. “If they get frost once they’ve budded, then it’s over.”

Wine grapes are more sensitive to extremes in weather, and climate change has caused some fluctuation.

“What we’ve noticed is these wild, crazy swings in the wintertime, super cold, and in the summer super dry,” said Glen Greiffendorf, the viticulturist and winemaker at 12 Corners Vineyard in Benton Harbor. “This year we had to trim the crop back some, just because there wasn’t enough water.”

St. Julian Winery in Paw Paw, one of the largest and oldest wineries in Michigan, has also experienced these negative changes.

“Early 2014 we saw temperatures dip to -20 F for more than four days at a time,” said Nancie Oxley, a winemaker at St Julian.

Most growers saw almost complete devastation on vitis vinifera varietals, such as riesling and chardonnay, and severe damage on the French-American varietals, such as baco noir and chancellor, according to Oxley. The year 2014 produced the smallest vintage that St. Julian had experienced in more than three decades.

It isn’t all bad though. Halfway through this year’s season, St. Julian’s harvest appears bountiful, Oxley said, and the varietals still on the vine look like they’ll turn out well too. That’s a consistent pattern for Michigan vineyards.

“Usually we’re happy to get two to three (years) in 10 that are super-perfect years where there’s not a lot of rain, not a lot of humidity and nice dry fall, and the harvest comes off real well,” Greiffendorf said. “We’ve probably been getting another extra one out of 10.”

The changes in climate have had good effects, and though frost is a problem, growers have ways to handle it.

“It’s getting better and better,” Sabbatini said. “Because we can choose varieties that ripen later, prune the vines differently, there are ways to fight the frost.”